It was one of the first things investigators removed last week from the wreckage of the collapsed truss crane at the I-280 Maumee River Crossing project - a little black box.
The “programming logic controller” (PLC) on the 2-million-pound crane is “the brains of the whole operation,” said Joe Rutherford, Ohio Department of Transportation spokesman.
As a result, investigators have told The Blade, it could hold critical clues to why the crane suddenly plummeted to the ground Feb. 16, killing four ironworkers and injuring four other workers.
Or it may not.
“It could be absolutely critical,” said Todd Audet, deputy director for ODOT District 2. “Or there might not be anything they can pull out of it.”
That's because investigators “don't know if it was damaged in the fall, damaged by the debris, or damaged by the weather,” explained Mike Gramza, ODOT project manager. The operating panel housing the controller broke open in the collapse and sat hanging from one of the piers - exposed to the cold and the elements - for a week before it was removed.
But the controller, manufactured by Germany-based Siemens and just larger than a Rubik's cube, is important enough that no one took any chances.
So before the plain black box was removed Tuesday - the first day investigators could navigate the precariously strewn equipment at the site - Siemens was contacted about the proper procedures and how to care for the device once it was removed.
Seimens' removal plan was then reviewed by an unnamed third party, with “no allegiances to ODOT, to Fru-Con [the project's general contractor], or to Siemens,” Mr. Rutherford said.
A representative from the third party accompanied a Siemens crewman into a lift, from where he oversaw the controller's removal from a larger control box dangling by cables 60 feet overhead from a pier, Mr. Rutherford said.
A second box, from the sister truss that remains in place, also was removed.
To maintain an official “chain of custody” required of any piece of evidence that may someday be the subject of civil or criminal litigation, the two boxes were placed in police hand and locked in the property room at police headquarters downtown.
“The steps we are taking to insure an honest and open and fair investigation are extensive and exhaustive,” Mr. Rutherford said.
But he and others warned against too much optimism.
“This is not like the black box you hear about in airplanes,” Siemens spokesman Paula Davis said. For one thing, she added, “there's no voice recorders.”
Still, she noted, programmable logic controllers record things such as side-to-side and up-and-down movements of cranes, as well as information on their weight load.
They're fairly common in the worlds of construction and transportation, said Raymond McCabe, a vice president with the American Segmental Bridge Institute and a senior vice president with HNTB, the project management consultant on the bridge.
PLC's are used in movable bridges, such as Toledo's Martin Luther King, Jr., lift bridge and in construction equipment, Mr. McCabe said.
“They make sure everything is done the same way every time and sequentially every time,” he said. Before PLC's came onto the picture more than a decade ago, he said, human controllers could misstep much easier.
Now, PLC's can sometimes provide clues to why a mishap occurred. For example, the devices can measures forces on the apparatus in question.
“You can almost diagnostically look at what might have happened,” he said.
Until its collapse, the $3 million crane made by the Italian firm Paolo de Nicola had worked so well the project was more than a year ahead of schedule.
The crane worked with two main components: an overbridge and an underbridge. The overbridge would be moved into place on erected piers, sliding over its underbridge, which would then move forward out of the way.
Once in position, the overbridge apparatus lifted precast segments, typically about 15 feet wide, into place. When the section was completed, the overbridge slid into its next position, repeating the cycle.
Crews had finished 11 of the 30 pairs of approach spans in East Toledo and were moving the cranes into position when it fell. The sister crane remained intact, and was moved back into position and locked down later that night. Officials repeatedly have said it will not be used again until they are certain of its safety.
For the past two weeks, they've taken frequent aerial photos, using stereoscopic photography to document changes to the site as wreckage is removed. They've photographed pieces of the wreckage up close, catalogued them, and marked them on a 200-point grid they're creating, and stored the pieces in a secure location, Mr. Rutherford said.
The Occupational Safety and Health Administration has said it might take weeks or months to determine the cause. Most of the 40 or so people investigators want to talk with have yet to be interviewed.
In the meantime, cleanup work continues with the goal of reopening the last closed section of I-280 northbound between Navarre Avenue (State Rt. 2) and Front Street by Friday.